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rummins 05-08-2008 04:54 PM

scf starter wireing help needed
hi all im new to this forum so please bare with me i brought an old 1970 atlas capco compressor but the starter isnt wired up on the motor its got 3ph but on the starter the plate says ph1 so i presume it must be single phase starter so my problem is how do i wire the starter up inside on top there are c/L3 on one side and on the other there is L2/L1 and at the front there is B/1/A and on the top there is 2 which is connected up to L1 i presume the single phase wires go to B/1/A but in what order i dont know so if anyone can please try to direct me in the right direction on where all the wires should go it would be a great help thankyou

micromind 05-08-2008 07:27 PM

We'll need a bit more info here; first, is the motor single or 3 phase? If this is a reciprocating compressor, then the motor nameplate will be easy to read. If it's a rotary screw, it'll be a bit tougher to get at.

Secondly, what is the power source? A single phase motor can be connected to a 3 phase system (if voltages match), but a 3 phase motor cannot be directly connected to a single phase system. A phase converter will be needed.

Eventually, we'll need the following info from the motor nameplate; HP, volts, full-load amps (FLA, or just plain amps, not service factor amps), and 1 or 3 phase. The size rating of the starter will also be needed, this has nothing to do with physical size, starters are rated as size 0, size 1, size 2, and so on. Don't sweat it if you can't find the starter size.

If you can give us the above info, we'll lead you through it, and make it run.


rummins 05-09-2008 02:05 AM

hi thanks for answering the plate on the motor states 1.1kw 1.5hp 2.5a 440v 3phase i think the amp are correct it could be 2-5 amp as plate got paint on there hope this helps thankyou the scf starter has on its plate type scf starter ph1 hp.5 volts 200/250 amps 3.5/4.2~5

rummins 05-09-2008 02:11 AM

sorry forgot to say it hasnt got a turn screw on the motor also i live in the uk so i need wire colours to match thankyou

rummins 05-09-2008 03:08 PM

hi wired up a different start/stop today put the wires going to the pressure switch the same way as they were before but still got same problem the compressor switches off long before it has reached pressure so i let out some air to see if it automatically restarts up but it doesnt i have to manually restart it by pushing the start button then it does the same again do you think the pressure switch has broke or may be the wires are wrong there are 4 wires going to the pressure switch they are brown/ black/ grey and earth thanks for looking the switch is a DANFOSS type PSU-9B

micromind 05-09-2008 09:55 PM

If there's a start-stop (2 pushbutton) control involved, you'll need another relay to make it work.

A start-stop works like this (I sure wish I could draw stuff on a computer!) power goes to one side of the stop button. It's normally closed (on). A jumper is installed from the other side of the stop button to one side of the start button, and one side of a contact on the starter. Both of these are normally open (off). The other side of the start button goes to the other side of the contact on the starter, and one side of the coil. The other side of the coil goes to the overload contact (if there is one), then on to the other side of the power.

When you press the start button, the coil is energized, the starter pulls in, and the contact pulls in as well. This simulates holding the start button in, and the coil will stay energized. When the stop button is pressed, current to the coil is interrupted, causing the starter to drop out, and the contact drops out as well. It will stay this way until the start button is pressed again.

If the pressure switch is wired in series with the stop button, once it's triggered, the start button will need to be pressed to get it going again. Obviously, this won't work very well. There are several solutions.

If you don't need to turn it off when not in use, simply get rid of the start-stop buttons and the starter contact, and wire the pressure switch in series with the control power and the coil. The pressure switch will turn the compressor on and off.

If you need to turn it off when not in use, the easiest way is to get rid of the start-atop buttons, and wire an on-off switch in series with the pressure switch, as described above. This way, if the on-off switch is off, the compressor won't run at all. If it's on, the pressure switch will turn it on and off.

If the start-stop must be used, it's a bit more complicated, and you'll need a small control relay. Basically, the control relay takes the place of the starter contact, and its output is wired in series with the pressure switch, then to the coil. One disadvantage to this type of control is that unless a pilot light is installed, you won't know if the compressor is off or controlled by the pressure switch.


rummins 06-20-2008 04:41 PM

Hi Sorry Its Been So Long.
I Have Decided To Use The Original Sfc Starter That Is On My Original Post, So Could Anyone Please Tell Me How To Wire This Up Please Using The Symbols That Are On The Unit . Thankyou

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